BTW, is gasgasinch the ONLY sealant to use on my timing cover gasket? Or will something like locktite 574 suffice?

Those Bosch starters are mighty rugged. I finally decided to refresh mine in my ‘78 R100. It had never been out of the bike. I THOUGHT it worked fine. I installed new plain bearings (soaked overnight in oil), new brushes, and brush springs, and gave it a general cleaning of course. And SHA-ZAAM!  What a difference it made!  Cranks much better, and I’ll bet with much reduced current draw. Most amazing part - it cost literally $15. 

And that's the deal, the OEM greases has oxidized and turned to a paste so thick that the motor can't turn. The bearings don't go "bad", they don't have enough hours on them. It's the grease inside the bearings that's gone "bad".

BTW, is Gasgasinch the ONLY sealant to use on my timing cover gasket? Or will something like LocTite 574 suffice?

I take it you mean the inner timing cover.

1. I use the BMW gaskets. Note there are 3 gaskets on that cover, and it's important you replace them all.
2. There is also an o-ring that gets replaced
3. There is also an oil seal that gets replaced
4. If you wish to supplement the BMW gaskets (which are VERY good) then you can thinly coat them with LocTite gasket maker before installation. Do so on all 3 gaskets equally.

If you remove the inner timing cover, then you should check your cam chain for wear. This is replaced as a set...

1. The chain
2. The tensioning blade (the idling blade should have nearly zero wear)
3. The tensioning blade plunger spring  (Note on the parts fiche, BMW updated the spring and so should you.)
4. And the chain master clip should have the closed end pointed in the direction of travel
5. And the alternator commutator brushes should always be checked/replaced.

• Removal of the inner timing cover is the best time to replace the 4 rubber mounts on the Rectifier Board with solid mounts.

• Sometimes the inner cover gasket electrically insulates the Rectifier from the remainder of the bike. Charging may be more reliable if you'll run a brown 14AWG wire from the "grounding corner" of the rectifier board to one of the fasteners in the starter compartment. (This wire takes the place of the short jumper used to connect across the rubber rectifier mounts.)

• And if your bike has the 3-prong ivory colored electronic ignition connector, the condition of that connector MUST be inspected very closely. Any crazing, cracking, or chipping and the connector MUST be replaced.

Hope this helps.

@grezer 

live had Millennium do cylinder work for me.   They do a super job.  They do fit the cylinder to the piston and will set ring end gap if you ask them.  

Ready to re-assemble carbs. Checking to make sure all passage-ways are clear. Everything is good down to the last two that are in the bottom of the throat , just behind the butterfly. When it opens a tiny bit they start to contribute. Not sure where to apply carb cleaner or air to determine if they are clear. Everywhere else a small bit of safety wire has worked...but those are too small.

Thoughts...

1. It's not so much the passages that get clogged, because the jets are much, much smaller. 
2. It's not a good idea to place anything metallic inside the jets. If you mush, then braided copper wire is the hardest thing. Smaller jets (#45 pilot jet) should simply be replaced.
3. The primary trouble spots for older carbs are the diaphragm because it is subject to splitting die to the Ethanol in the fuel, and the Needle setting because (unlike other brands of carbs) you cannot directly see which "notch" the clip is set in. I suggest you check both slides for equal Needle extension.
4. The enrichener jet in the bottom of the float bowls will need to be clear.
5. After the timing is set with an ignition strobe lamp, the carbs will need to be balanced with some sort of manometer or carb vacuum device. 

   Hope this helps.